I have 4 desktops and one activity per desktop.

Some desktops have duplicate menu items. Some are normal:

Example of a normal one on Desktop 2


Example of a duplicated menu on desktop 1:


What causes this? How can it be prevented?

Ouch. Thats a bug in Plasma, which needs to be reported at bugs.kde.org if you're using KDE 4.3.

I've the same issue.
What files do I have to delete to clean my plasma-desktop conf (Plasmoids, activities, etc)?

Howl wrote:I've the same issue.
What files do I have to delete to clean my plasma-desktop conf (Plasmoids, activities, etc)?

/home/username/.kde/share/config/plasma*

In some distros .kde is for kde3 though, and it's instead .kde4

After cleaning my plasma conf this glitch seemed gone away but now it is back.
Maybe it's fault of "one activity per desktop" option.

After deleting /home/username/.kde/share/config/plasma*
and starting over I got this fairly well under control and haven't seen it return.

First you can't delete activities until you UnCheck different activities per desktop.
Then delete all bogus activities that you don't want. You will always end up with ONE that you can't get rid of.

Then check Different activities per desktop and (if you have 4 desktops) you will see 4 new activities. Configure each as you like and you should be good.

There is one thing to look out for: If your machine has two monitors, you will often see twice as many activities as desktops. Since I was working in a Vmware machine and had not Limited the machine to a single monitor, I was getting two activities every time I added one. I forced Vmware to only allow the Virtual machine running Linux to see a single monitor and so far it is stable.

It's exactly what i've done but it didn't do the trick.
Anyway, i will retry later.